1 More Comments on the SM&C Core Service Red Book, Issue 0.1 Takahiro Yamada, JAXA/ISAS 27 October, 2004

2 More Comments I fully agree that service specifications are about logical interactions and have nothing to do with physical deployment. This Red Book does not have to show how the SM&C Core service should be physically deployed. However, space data systems are always distributed systems and we must show, in some place (and probably not in the Service Red Book), how services are physically deployed in the systems. I use box-oval diagrams to illustrate how services can be physically deployed in a system, and it does not have to be in the Service Red Book but it must exist somewhere. Boxes are physically separate elements. That's why they need communications protocols to communicate with each other.

3 A Typical Example A typical example of the box-oval notatioin is the following. Spacecraft X-ray Camera M&C Middleware Comm. Protocols Ground Control Center X-ray Operations Application M&C Middleware Comm. Protocols

4 Where is the Service? Let’s take the service for limit checking for example. The problem is where limit checking is performed. In the previous example, it is performed by the ground M&C middleware. The service is, in a logical sense, provided by the green layer for the blue layer. Therefore, the green layer is the service provider and the blue layer is the service consumer in this diagram. In the physical reality, however, the onboard M&C middleware collects necessary data from the camera and send it to the ground M&C middleware, and the ground M&C middleware performs limit checking and delivers the result to the operations applications.

5 Controller and Target Controller and Target are the roles that entities play. They both use the M&C service. This is like both the FTP server and the FTP client use the transport service provided by TCP. In the previous example, the spacecraft (specifically the camera) plays the role of Target, and the ground (specifically the ops. application) plays the role of Controller. Therefore, Controller and Target are not the same as the M&C service provider and consumer.